In recent years, cases where data delivery of large capacity file is required have been increased. For example, moving pictures (movie, video, television program, etc.) which could been only handled as analog data in the prior art are being digitized. In general, in the case where moving picture is digitized, capacity of file becomes very large. For this reason, in digital broadcasts such as typical television broadcast, etc., such digital data of large capacity are transmitted in compressed state. In the case of ordinary broadcast, the compression system such as MPEG2 or MPEG4 is used so that data quantity is compressed into one several tenth. Digital data compressed in this way are caused to undergo transmission through existing one transmission path, e.g., one transponder in the case of satellite.
However, in the conventional data delivery, there is the problem that it is difficult to carry out transfer of file of large capacity or relaying of video of high picture quality.
For example, in the case of carrying out business data delivery such as delivery of movie, etc., it is necessary to suppress degradation of picture quality by transmission as small as possible unlike typical television broadcast. For this reason, compression factor must be held down to value lower than that in the ordinary case. As a result, capacity of file to be subjected to transmission becomes very large.
For example, data capacity that one transponder can carry out transmission is about 30M bps. In order to carry out transmission of video of picture quality of HDTV (High Definition Television) of 2 hours in non-compressed manner, 66 hours are required. For this reason, it was impossible to respond to, e.g., needs to carry out transmission of file overnight.
In addition, also in data transmission of real time such that relaying of video is carried out, it is impossible to carry out transmission of data at such a transmission rate to exceed capacity of one transmission path. For this reason, it was impossible to respond to needs to deliver moving picture data while maintaining high picture quality.